The present invention relates to improvements in optical sensing techniques and systems, and more particularly to improvements in techniques for providing frequency selectivity and tracking in optical radar systems.
Conventional optical radar systems generally utilize a source of optical energy radiating at a known frequency and directed towards a given target. The reflected radiation is then sensed by a receiver-detector system which uses the information in the reflected beam to perform such functions as ranging and tracking of a target. The success of the optical sensing system depends on the ability of the receiver to be tuned to receive the reflected beam usually generated at a fixed frequency.
Known methods and apparatus have been deficient due to the problems encountered in precisely controlling the generated frequency and in providing frequency isolation by filtering in the receiving system. Even where frequency generation and reception have been precisely controlled, the ability to provide systems adjustable over a range of frequencies such that tracking of the transmitted beam occurs, has been very limited or unknown.
The particular significance of such deficiencies might best be appreciated where the optical systems are utilized in the presence of noise or interfering radiation. Since the ability of the system to be used as an optical radar depends on the isolation of a given signal frequency by the receiver circuits, the presence of noise would interfere significantly where precise filtering is not available. In addition, where only a single frequency is used, the system becomes highly vulnerable to interfering or jamming radiation.
Accordingly, the present invention has been developed to overcome the specific shortcomings of the above known and similar techniques and to provide a more secure optical sensing system having highly selective frequency generation and signal tracking.